1: With it being new (or only a few weeks old), the battery may not be calibrated correctly. It's not like a gas tank that can be "measured" with a float or sensor. This is why some people have recommended in the past to run the battery down a couple times before using it normally. Nothing to do with the health of the battery, but to let the parts of the charging system that reads the battery level, learn min/max levels. It could be that it thought it had 36% left when it really didn't.

2: It's got a bad cell in the battery. It should have 36% left (see above), but the cell is faulty and doesn't hold a charge. If it's new it should be replaced. This becomes much more common as the battery ages, and is usually taken into account as a quicker drop in available % (again, see above).